# Mathematics of Computation

Published by the American Mathematical Society, the Mathematics of Computation (MCOM) is devoted to research articles of the highest quality in all areas of pure and applied mathematics.

ISSN 1088-6842 (online) ISSN 0025-5718 (print)

The 2020 MCQ for Mathematics of Computation is 1.98.

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## On generalized averaged Gaussian formulas. IIHTML articles powered by AMS MathViewer

by Miodrag M. Spalević
Math. Comp. 86 (2017), 1877-1885 Request permission

## Abstract:

Recently, by following the results on characterization of positive quadrature formulae by Peherstorfer, we proposed a new $(2\ell +1)$-point quadrature rule $\widehat G_{2\ell +1}$, referred to as a generalized averaged Gaussian quadrature rule. This rule has $2\ell +1$ nodes and the nodes of the corresponding Gauss rule $G_\ell$ with $\ell$ nodes form a subset. This is similar to the situation for the $(2\ell +1)$-point Gauss-Kronrod rule $H_{2\ell +1}$ associated with $G_\ell$. An attractive feature of $\widehat G_{2\ell +1}$ is that it exists also when $H_{2\ell +1}$ does not. The numerical construction, on the basis of recently proposed effective numerical procedures, of $\widehat G_{2\ell +1}$ is simpler than the construction of $H_{2\ell +1}$. A disadvantage might be that the algebraic degree of precision of $\widehat G_{2\ell +1}$ is $2\ell +2$, while the one of $H_{2\ell +1}$ is $3\ell +1$. Consider a (nonnegative) measure $d\sigma$ with support in the bounded interval $[a,b]$ such that the respective orthogonal polynomials, above a specific index $r$, satisfy a three-term recurrence relation with constant coefficients. For $\ell \ge 2r-1$, we show that $\widehat G_{2\ell +1}$ has algebraic degree of precision at least $3\ell +1$, and therefore it is in fact $H_{2\ell +1}$ associated with $G_\ell$. We derive some interesting equalities for the corresponding orthogonal polynomials.
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